1. Field of the Invention
The present invention is method for aligning bi-refringent waveguides and more particularly a method for using an interferometer sensitive to rotational misalignments between bi-refringent waveguides to make precise rotational alignments of such waveguides.
2. Description of the Prior Art
Bi-refringent waveguides are used extensively for interferometer applications such as the fiber optic gyroscope. Examples of bi-refringent waveguides would be polarization maintaining fiber and integrated optics circuits. The performance of the fiber optic gyro is a direct function of the rotational misalignments between the refractive index axes of the bi-refringent waveguide sections which comprise the optical circuit. It is, therefore, imperative to obtain the proper rotational alignment between the waveguide sections before the joining process is implemented.
Presently, fiber to fiber, fiber to waveguide, and fiber to chip alignments (.theta.) or extinction characterization (.epsilon.) are made by an intensity measurement using a polarizer/analyzer set-up. The disadvantages of the above techniques are that under the most favorable conditions, the limit of resolution is approximately 1.degree. or extinction measurements of -35 dB.
The present invention successfully addresses the above shortcoming and deficiencies as follows:
The output of the invention is a function of .theta. or .epsilon. instead of .theta..sup.2 or .epsilon..sup.2 as in the intensity measurement. This gives the invention its superior resolution limit.
It is thus an object of the present invention to provide a method for reliably and precisely aligning bi-refringent optical waveguides.
It is yet another object of the present invention to provide a method for aligning bi-refringent optical waveguides to an accuracy of &lt;0.2.degree..
It is still another object of the present invention to provide a method for aligning bi-refringent optical waveguides interferometrically.
It is another object of the present invention to minimize or eliminate coherence feature introduction and adverse effect in the process of alignment of bi-refringent fibers and waveguides.
It is finally another object of the present invention to provide a method of performing extinction measurements more accurately than with intensity measurements.